As one of biometric authentication methods, there is a one-to-N authentication method. The one-to-N authentication method is a method in which, even if there is not information for identifying a user, such as the ID or the like of the user who is a verifier, individual authentication is performed by comparing the biometric data of the user with the preliminarily stored reference biometric data of a plurality of users.
In the one-to-N authentication method, when the number of pieces of the reference biometric data stored in a database increases, there is increased the likelihood that input biometric data becomes similar to the reference biometric data of another user. Accordingly, a false acceptance rate at the time of authentication is increased, and there is increased a risk that an individual is authenticated as the other user.
For example, there is a technique in which a list of biometric information registration data having the high degree of similarity is preliminarily prepared and only when biometric data is similar to the listed registration data at the time of the execution of authentication, an individual judgment threshold value is strictly changed and authentication is performed. An example of such a technique is disclosed in Japanese Laid-open Patent Publication No. 2005-182184.
In addition, for example, there is a technique in which individual judgment threshold values are provided in units of registration data and when there are a plurality of pieces of registration data where the degrees of similarities to pieces of biometric information inputted from a user exceed a threshold value, individual judgment threshold values corresponding to these pieces of registration data are strictly realigned. An example of such a technique is disclosed in Japanese Laid-open Patent Publication No. 2008-243054.
However, in the above-mentioned techniques, while the individual judgment threshold values are strictly realigned and it is possible to reduce a false acceptance rate, a false rejection rate increases and an authentication success rate decreases.